Validity and reliability of the activPAL3 for measuring posture and stepping in adults and young people

doi:10.1016/j.gaitpost.2015.10.020

Gait & Posture

Volume 43, January 2016, Pages 42-47

https://doi.org/10.1016/j.gaitpost.2015.10.020 Get rights and content

Highlights

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The activPAL3 is valid for the detection of posture and purposeful stepping.
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Posture detection was excellent for standardised activities.
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Only purposeful steps during activities of daily living were detected by the monitor.
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The activPAL3 demonstrates good to excellent (ICC(1,1)) inter-device reliability.

Abstract

Characterisation of free-living physical activity requires the use of validated and reliable monitors. This study reports an evaluation of the validity and reliability of the activPAL3 monitor for the detection of posture and stepping in both adults and young people. Twenty adults (median 27.6y; IQR22.6y) and 8 young people (12.0y; IQR4.1y) performed standardised activities and activities of daily living (ADL) incorporating sedentary, upright and stepping activity. Agreement, specificity and positive predictive value were calculated between activPAL3 outcomes and the gold-standard of video observation. Inter-device reliability was calculated between 4 monitors. Sedentary and upright times for standardised activities were within ±5% of video observation as was step count (excluding jogging) for both adults and young people. Jogging step detection accuracy reduced with increasing cadence >150 steps min⁻¹. For ADLs, sensitivity to stepping was very low for adults (40.4%) but higher for young people (76.1%). Inter-device reliability was either good (ICC(1,1) > 0.75) or excellent (ICC(1,1) > 0.90) for all outcomes. An excellent level of detection of standardised postures was demonstrated by the activPAL3. Postures such as seat-perching, kneeling and crouching were misclassified when compared to video observation. The activPAL3 appeared to accurately detect ‘purposeful’ stepping during ADL, but detection of smaller stepping movements was poor. Small variations in outcomes between monitors indicated that differences in monitor placement or hardware may affect outcomes. In general, the detection of posture and purposeful stepping with the activPAL3 was excellent indicating that it is a suitable monitor for characterising free-living posture and purposeful stepping activity in healthy adults and young people.

Introduction

Whilst laboratory-based observation of human movement can tell us what a person is capable of, it is necessary to make recordings within the person's free-living environment to develop an understanding of what they actually do. The measurement of this activity must be performed using instruments with demonstrated validity and reliability [1].

The activPAL activity monitor is a uni-axial activity monitor manufactured by PAL Technologies Limited, Glasgow, UK, with demonstrated validity and reliability for characterising posture and measuring stepping for adults [2], [3], [4], older adults [5], pre-school children [6], 9–10 year olds [7] and female adolescents [8], [9].

The activPAL3 monitor, produced by the same company, contains a tri-axial accelerometer. It outputs a different range of raw acceleration and uses a higher sampling frequency and subsequently different hardware filtering compared to the earlier version of the activPAL. Therefore, demonstrated validity and reliability of the activPAL may apply to the activPAL3. Despite claims that the activPAL3 has been “widely validated” [10], only limited reports in adults are available. Berendsen et al. [11] report 100% validity for detecting posture type/walking time for 5 adults (22.4 ± 2.2y) performing a highly controlled protocol eliminating transitions between activities. Stansfield et al. [12] reported step counting accuracy during treadmill walking, demonstrating that steps are accurately counted above 0.5 m s⁻¹. However, they reported only a limited range of stepping speeds also with transitions removed. Ryde et al. [13] studied office workers for a short standardised protocol involving sitting and standing (3–60 s duration) and 1 h of free-living office duties. They reported excellent agreement between direct observation and activPAL3 for sitting time and number of sit-to-stand transitions [13]. To enhance our understanding of the validity and reliability of the activPAL3, a protocol must be used which examines not only controlled standardised testing, but also incorporates elements of choice of movement pattern and activities, similar to a range of free-living conditions. There is also a need to expand the validation to children and adolescents, where differences in outcome may be expected due to smaller size and different movement pattern compared to adults.

The primary aims of this study were to determine the validity and inter-device reliability of the activPAL3 in measuring posture and stepping of adults and young people with unimpaired mobility. To enhance the generalisability of outcomes to activity in free-living environments, protocols involving typical activities of daily living with partial free-choice were incorporated [3], [4].

Section snippets

Participants

Two convenience samples were recruited from university staff, students and their families:

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Adults: 20 participants aged 18–65 years.
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Young People: 8 participants aged 6–17 years.

Participant numbers were recruited in line with previous study populations (5–30 per group) [2], [3], [7], [9], [11], [12], [13]. Participants had to be able to walk independently without mobility aids, carry out everyday tasks and leisure time activities independently and walk for 40 min within 80 min. Ethical approval was

Results

Twenty adults (9M, 11F) (median age 27.6y (IQR 22.6), mean height 172.4 ± 9.0 cm, weight 73.3 ± 13.0 kg, BMI 24.6 ± 3.2 kg m⁻²) and 8 young people (2M/6F) (mean age 12.0 ± 4.1y, height 152.4 ± 25.0 cm, weight 42.3 ± 16.4 kg) took part. All young people were normal weight. Self-selected walking speeds were: Adults slow 0.98–1.61, normal 1.30–1.88, fast 1.61–2.24, treadmill jogging 1.4–3.0, outside jogging 2.2–4.1 m s⁻¹; young people slow 0.92–1.53, normal 1.08–1.72, fast 1.53–2.06, treadmill jogging 2.1–2.9,

Discussion

It is necessary to be cautious in assuming that new or ‘upgraded’ monitors, with different hardware and software, produce the same outcomes as older monitors. Therefore, new physical activity monitors must be assessed for validity and reliability, ideally under conditions representative of their intended use. To achieve this aim for the activPAL3, the current study implemented both a standardised, controlled protocol and an ADL, relatively self-selected, protocol. The assessment of the

Conflict of interest statement

This work was funded jointly by the UK Engineering and Physical Sciences Research Council (EPSRC) (Grant reference EP/G501416/1) and PAL Technologies Ltd (Glasgow, UK) as part of a CASE PhD Studentship award. PAL Technologies Ltd is the manufacturer of the activPAL3, the device used in this study. Ceri Sellers was the funded PhD student and Ben Stansfield and Philippa Dall were named Investigators on the award. PAL Technologies Ltd had no involvement with the design, collection, analysis or

Acknowledgements (funding)

The work completed here was funded as part of an EPSRC CASE PhD studentship award (Grant reference EP/G501416/1) which was partly funded by PAL Technologies Ltd (Glasgow, UK), the manufacturer of the activPAL3 device. The authors would like to thank all participants for their time in taking part in this work.

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Citation Excerpt :
Kim et al. [31] indicated that the activPAL underestimated light, moderate, and vigorous physical activity compared to indirect calorimetry (overall, MAPE = 27.4%). As shown in Table 3, 17 study arms were conducted in semi-structured conditions [22–25,27,39–50]. Similar to laboratory protocols, most studies observed the activPAL as a valid measure of step count (n = 7/9, no fixed bias and MAPE < 3%), step cadence (n = 3/3, no fixed bias), and stepping time (n = 5/6, absolute percent error < 3% and % agreement > 93%).
Accumulating step counts and engaging in moderate-to-vigorous intensity physical activity is positively associated with numerous health benefits. The activPAL is a thigh-worn monitor that is frequently used to measure physical activity.
Can the activPAL accurately measure stepping activity and identify physical activity intensity?
We systematically reviewed validation studies examining the accuracy of activPAL physical activity outcomes relative to a criterion measure in adults (>18 years). Citations were not restricted to language or date of publication. Sources were searched up to May 16, 2021 and included Scopus, EMBASE, MEDLINE, CINAHL, and Academic Search Premier. The study was pre-registered in Prospero (ID# CRD42021248240). Study quality was determined using a modified Hagströmer Bowles checklist.
Thirty-nine studies (20 laboratory arms, 17 semi-structured arms, 11 uncontrolled protocol arms; 1272 total participants) met the inclusion criteria. Most studies demonstrated a high validity of the activPAL to measure steps across laboratory (12/15 arms), semi-structured (10/13 arms) and uncontrolled conditions (5/7 arms). Studies that demonstrated low validity were generally conducted in unhealthy populations, included slower walking speeds, and/or short walking distances. Few studies indicated that the activPAL accurately measured physical activity intensity across laboratory (0/6 arms), semi-structured (0/5 arms) and uncontrolled conditions (2/5 arms). Using the default settings, the activPAL overestimates light-intensity activity but underestimates moderate-to-vigorous intensity activity. The overall study quality was 11.5 ± 2.0 out of 19.
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Gross Motor Functional Classification System (GMFCS) level was determined by validated self‐report questionnaire. Activity (daily step count, walk time, sitting time, standing time, and transitional movements) over 6 days recorded using an activPAL. Weight, body mass index (BMI), and waist-to-hip ratio were measured. Bivariate relationships between anthropomorphic and activity measures were assessed.
Thirty-eight participants completed all measurements. Nine were excluded because of incomplete activPAL data. The median age was 28.50 years (interquartile range [IQR]=24.25-47.00), range 18-77 years. Participants’ GMFCS levels were I: 13%; II: 16%; III: 21%; IV: 34%; and V: 16%. Median steps/day for GMFCS I/II participants were 5258.3 (IQR=3606.8-6634.7), and median steps/day were 1681.3 (IQR=657.2-2751.8) and 30.0 (IQR=6.8-54.2) for GMFCS level III and IV/V participants, respectively. Significantly greater steps/day were found for GMFCS I/II or III participants compared to those GMFCS IV/V (P<.001 and P=.0074, respectively). In addition, 60.5% of the subjects had a BMI in the normal range, 10.5% were obese, 23.6% were overweight, and 5.3% were underweight. For subjects with GMFCS I/II, the Spearman's rank correlation coefficient for time standing and waist circumference was −0.73 (0.01). GMFCS III and GMFCS IV/V participants had respective correlations of −0.16 (0.71) and −0.01 (0.98). For subjects with GMFCS I/II, the Spearman's rank correlation coefficient for standing time and BMI was −0.55 (P=.08). For the GMFCS III and GMFCS IV/V groups the respective correlations were −0.19 (0.67) and 0.00 (1.00).
Subjects with GMFCS level I or II who engaged in more activity tended to have more favorable anthropometric profiles. Subjects with GMFCS level III, IV, or V did not have a similar trend. Our findings suggest factors beyond activity patterns affect anthropometrics to a greater degree in those with higher GMFCS levels.
Validity of the ActivPAL monitor to distinguish postures: A systematic review
2022, Gait and Posture
Posture has been recently integrated into activity guidelines, advising people to limit their sedentary time and break up sedentary postures with standing/stepping as much as possible. The thigh-worn activPAL is a frequently used objective measure of posture, but its validity has only been investigated by individual studies and has not been systematically reviewed.
Can the activPAL accurately characterize different postures?
A rigorous systematic review protocol was conducted, including multiple study screeners and determiners of study quality. To be included, validation studies had to examine the accuracy of an activPAL posture outcome relative to a criterion measure (e.g., direct observation) in adults (>18 years). Citations were not restricted to language or date of publication. Sources were searched on May 16, 2021 and included Scopus, EMBASE, MEDLINE, CINAHL, and Academic Search Premier. The study was pre-registered in Prospero (ID# CRD42021248240). Study quality was determined using a modified Hagströmer Bowles checklist. The results are presented narratively.
Twenty-four studies (18 semi-structured laboratory arms, 8 uncontrolled protocol arms; 476 participants) met the inclusion criteria. Some studies (5/24) incorporated dual-monitor (trunk: 4/5; shin: 1/5) configurations. While heterogenous statistical procedures were implemented, most studies (n = 22/24) demonstrated a high validity (e.g., percent agreement >90%, no fixed bias, etc.) of the activPAL to measure sedentary and/or upright postures across semi-structured (17/18 arms) and uncontrolled study designs (7/8 arms). Specific experimental protocol factors (i.e., seat height, fidgeting, non-direct observation criterion comparator) likely explain the divergent reports that observed valid versus invalid findings. The study quality was 11.3 (standard deviation: 2.3) out of 19.
Despite heterogeneous methodological and statistical approaches, the included studies generally provide supporting evidence that the activPAL can accurately distinguish between sedentary and standing postures. Multiple activPAL monitor configurations (e.g., thigh and torso) are needed to better characterize sitting versus lying postures.

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Full length ArticleValidity and reliability of the activPAL3 for measuring posture and stepping in adults and young people

Highlights

Abstract

Introduction

Section snippets

Participants

Results

Discussion

Conflict of interest statement

Acknowledgements (funding)

Med Eng Phys

Med Eng Phys

Arch Phys Med Rehabil

Medical statistics: a common sense approach

The validity and reliability of a novel activity monitor as a measure of walking

Br J Sports Med

The validation of a novel activity monitor in the measurement of posture and motion during everyday activities

Br J Sports Med

Measuring postural physical activity in people with chronic low back pain

J Back Musculoskelet Rehabil

Activity-monitor accuracy in measuring step number and cadence in community-dwelling older adults

J Aging Phys Act

Validity: practical utility, and reliability of the activPAL in preschool children

Med Sci Sports Exerc

Examining the validity of the activPAL monitor in measuring posture and ambulatory movement in children

Int J Behav Nutr Phys Act

Full length Article
Validity and reliability of the activPAL3 for measuring posture and stepping in adults and young people